Scroll chuck thread

[surfdabbler]

I'm looking at purchasing a scroll chuck soon, but having difficulty with the thread size.

I have an old (very old - late 1800s) metalwork lathe that I am using for woodturning. The lathe came with a few chucks, but the self-centering chuck is a huge metalwork jobby that weighs about 10kg, and I'm concerned about using it long term.

I'd like to get a nice Vicmark or Teknatool style chuck to replace it, but unless I'm measuring wrong, I can't get a threaded insert to fit my lathe.

Measuring the lathe, the drive thread is roughly 15/16 of an inch diameter. It's actually tapered slightly, 24.5mm (31/32") down to 23.5mm (15/16") at the end. The thread is 8TPI. 1" seems to be a pretty standard size for the drive thread, but mine is definitely less than 1". Now, my question is...Is it common for a 1" drive thread to measure less than 1"? Or have I got some weird non-standard thread that's not going to fit anything? I would think it has to be some sort of standardised thread, as I have a couple of different non-original chucks.

[Paul39]

Surfdabbler,

I expect that in over 100 years of putting on and taking off chucks and face plates the 1 X 8 tpi thread is worn a bit.

As the position of the chuck on the spindle is usually determined by the flats on the face of the spindle and back of the chuck, or sometimes a recess on the chuck fitting a non - threaded part of the spindle, I think a 1 inch by 8 tpi chuck insert would fit fine.

You could buy an insert for the chuck you expect to get and try it, or if there is an engineers supply nearby, get a grade 8 (more expensive, better finished, much stronger, made to closer tolerance) nut to try. If the insert or nut pulls up snugly on the spindle nose, you are in business.

If the chuck is not perfectly centered on the spindle, all is not lost as the bowl will be perfectly round even though the recess or spigot may not be perfectly centered. A few thousandths of an inch will not be noticed.

How about a photo of the lathe. I like the design of old machinery.

[Treecycle]

Agree totally with what Paul39 has said. A 1" thread will never measure 1" as there needs to be clearance when fitting the female (nut) part of the thread on, so the tips of the thread are removed before the thread is cut. A good quality nut to check the thread is a very good suggestion. The better quality nuts in mild steel are often referred to as machned nuts here.

[surfdabbler]

The thread still looks very good, so I hadn't thought of wear, but perhaps you are correct. The lathe hasn't had a very hard life of use. If anything, it's had a hard life of long periods of neglect. But I've cleaned it up, and it's all running pretty nicely at the moment.

Here's a couple of photos, before and after restoration. (The tailstock and cross-slide aren't in the first photo, but they were pretty badly rusted before hand).

With the lack of 1" machine nut handy, I'll probably just get a chuck with a 1" fitting, and work out what to do later if it doesn't fit.

[Paul39]

Surfdabbler,

That is lovely. I think I see a plate on it. Does it have a name? If so you might find more information here:

http://www.lathes.co.uk/

Over here some antique dealers buy lathes like that and make fancy tables using the legs and scrap the rest.

I think a 1 X 8 tpi chuck will fit nicely on that.

[Hermit]

The thread still looks very good, so I hadn't thought of wear, but perhaps you are correct. The lathe hasn't had a very hard life of use. If anything, it's had a hard life of long periods of neglect. But I've cleaned it up, and it's all running pretty nicely at the moment.

Here's a couple of photos, before and after restoration. (The tailstock and cross-slide aren't in the first photo, but they were pretty badly rusted before hand).

With the lack of 1" machine nut handy, I'll probably just get a chuck with a 1" fitting, and work out what to do later if it doesn't fit.

Maybe there's someone close by with a 1" x 8tpi insert that you can try.

[surfdabbler]

Does it have a name?

I haven't named it yet. Perhaps I will call it Patsy.

I've looked into the history, and it's a WF&J Barnes #5 Screw-cutting lathe.

[China]

Do you have the original cross slide etc. if so buy a blank insert and cut the thread yourself

[DaveTTC]

nice looking lathe I must say


Dave the turning cowboy

turning wood into art

[Oldgreybeard]

You have done a good job on cleaning it up - Is painting on the horizon?

You should be able to buy a 1" 8 tpi nut at virtually any industrial supply shop to check the fit before investing in a chuck - should only be a couple of dollars.

Bob

[Evanism]

If one of the chucks still fit, why not take that to the Nut n bolt supplier and get them to try various bolts to see which fits.

You will know for certain what thread it was supposed to be originally. You can work from there....

[Paul39]

Surfdabbler,

Some info on Barnes lathes:

http://vintagemachinery.org/photoind....aspx?id=14467

http://www.lathes.co.uk/barnes/

As it is a US made lathe, the 1 X 8 tpi spindle thread is common as dirt for that size of metal and wood lathe here.

In this:

http://www.practicalmachinist.com/vb...g-help-114855/

Post 12 says the lathe has a 1 X 8 tpi spindle.

I think you can expect a 1 inch X 8 tpi insert or direct mount chuck to fit. The advantage of a chuck with insert is that if you buy a different lathe you can change lathe spindle sizes and use the same chuck.

See also: http://www.teknatool.com/support/how...e%20thread.htm